Self-venting liquid drain valves have been known in the art for many years. Specifically, various assemblies have been made to provide fluid drainage from a vessel while providing a separate inlet for gas, such as air, to replace the fluid being drained. For example, in fuel/water separators used in diesel engines, water must be periodically drained using a valve assembly adapted to feed air into a separator while the water is being drained. The prior art devices have accomplished this by providing separate air and liquid passages formed through a portion of the valve assembly member.
U.S. Pat. No. 4,440,193 issued to Matheson and assigned to the same assignee (Cummins Engine Company, Inc.) as the present invention discloses a valve assembly for draining a liquid including a valve housing or body member 23 adapted to receive a threaded valve piece 24 rotatably movable between open and closed positions. An air intake passage is contained within body member 23 separate from the liquid drain passage contained in movable valve piece 24. This type of arrangement requires separate sealing means for the air intake passage and the liquid drain passage.
U.S. Pat. No. 4,708,171 issued to Cudaback attempted to simplify the prior art valves by including both the air inlet and liquid passages in a single valve member rotatable between open and closed positions. However, the drain valve disclosed in Cudaback requires a rather complicated valve housing secured to a vacuum vessel and adapted to provide a close fit between the housing and the valve member to ensure proper liquid drainage through radially extending openings at the upper end of the housing. The air inlet passage also requires a sealing point within the housing to prevent gas from entering the vessel when the valve assembly is closed.
Eidsvoog et al. U.S. Pat. No. 4,611,627 discloses a self-venting drain valve with a valve portion 16 movable relative to housing 14 including an air intake 26 and a water passage outlet 34. This device, however, requires at least two different seals (44 and 52), and the intake passage 26 is provided entirely within the non-moving housing 14.
Iketani U.S. Pat. No. 3,044,504 discloses a valve with an axial opening which bends 90 degrees to the side (at 15) and a second passage 12. However, this device is directed to an injector valve that requires at least two seals 13 and 14.
Matheson et al. U.S. Pat. No. 4,753,266, assigned to the same assignee of the present invention, discloses another valve assembly having two passages 26, 27, one for draining liquid and another serving as an air vent. Valve member 22 is rotatably mounted on body member 21, but the rotation is limited to 90.degree.. The valve member rotates so that its passages 32, 33 engage passages 26, 27 when the valve is open. Three 0-ring seals are used to seal the two passages and the valve assembly to the vessel.
The prior art fails to accomplish or teach draining liquid from a vessel using a simple valve assembly requiring minimal manufacturing and replacement costs.